The increasing world population has led to a rising demand for food, energy, and natural resources. Food production is closely related to water availability. Water, once available in much of the earth's surface, is the limiting factor in agricultural productivity. Thus, the steady increase of agriculture, together with climate change, is making the use of water resources unsustainable. In this scenario, a need exists to increase agricultural productivity in a sustainable manner, that is, to produce more using less water (Morison et al., 2008; FAO, 2012). Another problem to be faced is the availability of areas for cultivation because, increasingly, these areas are scarce and a great concern exists for the conservation and preservation of biodiversity.
Many efforts are being made to reduce the amount of water used for agriculture, and to produce “more by drop” and per hectare. One way to achieve that increased agricultural productivity can be through plant breeding. In such a way, it is possible to increase yield, but also minimize losses by biotic and abiotic stresses (Morison et al., 2008; Parry and Hawkesford, 2012).
However, to improve plant growth, intervention in the cell cycle of the plant is often needed. As it is well known, the cell cycle is a conserved and critical step in the life cycle of eukaryotic organisms where the genetic material from the mother cell is duplicated and divided between two daughter cells. This process is coordinated with changes in the architecture of the cell and has four well-defined stages: the stage of synthesis, mitosis and two intervals, known as gap1 (G1) and gap2 (G2).
In the synthesis phase (S phase), the DNA is replicated to produce copies of the two daughter cells. During the G2 gap, new proteins are synthesized and the cell doubles in size. Later, in mitosis (M phase), the replicated chromosomes are separated so that each daughter cell receives a copy.
In the interval between mitosis and DNA synthesis phase (G1 gap), nuclear DNA is prepared for replication.
Errors in this cycle progression could have serious consequences for the integrity of the genome and, therefore, for the development of the organism. Thus, to ensure that the events occur properly and the DNA is duplicated only once, the cells have checkpoints between transitions (Ramires-Parra et al., 2005; Berkmans and de Veylder, 2009; de Veylder et al., 2007).
The first checkpoint determines whether the cell enters the DNA synthesis phase (G1) or remains in the quiescent state. The first step of the DNA synthesis phase is the formation of a structure that will regulate the entire process of cell division, the pre-replicative complex (pre-RC) (Machida et al., 2005; M. I. Aladjem, 2007).
The first step in the formation of the pre-RC is the recognition of DNA replication origins by the Origin Recognition Complex (ORC). After this recognition, the CDC6 and CDT1 proteins join the ORC complex and will recruit the MCM complex, which has helicase activity, culminating in the licensing of DNA for replication (Machida et al., 2005; Blow and Dutta, 2005; Sun and Kong, 2010).
It was revealed in an article by our group (H. P. Masuda, L. M. Cabral, L. De Veylder, M. Tanurdzic, J. De Almeira Engler, D. Geelen, D. Inze, R. A. Martienssen, P. A. Ferreira, and A. S. Hemerly—ABAP1 is a novel plant protein armadillo BTB involved in DNA replication and transcription, EMBO Journal, 2008), that Arabidopsis thaliana has a new cell cycle regulation mechanism in which the ABAP1 protein plays a central role. This protein interacts with members of the DNA replication machinery, transcription factors and other classes of proteins (Masuda et al., 2008). One of these proteins with which ABAP1 interacts was called AIP10. Knockout plants for AIP10 gene have larger roots and leaves, produce more seeds and have greater resistance to water stress situations.
Other research and disclosures have also been made to promote increased plant biomass, however, by different methods. For example, International Application WO 2011/130815, the contents of which are incorporated herein by this reference, discloses a method for increasing plant biomass by introducing a polynucleotide sequence into the plant genome.
Through the use of recombinant DNA, in the patent application EP2295582, the contents of which are incorporated herein by this reference, the inventor seeks the enhancement of plant specimens by controlling nucleic acid expression of CDC27A. The disclosure described in the application WO 2004/029257, the contents of which are incorporated herein by this reference, seeks to alter the development of a plant.
The patent EP2391642, the contents of which are incorporated herein by this reference, refers to a protein complex that promotes plant growth. More specifically, the disclosure relates to the use of specific proteins of the anaphase-promoting complex/cyclosome to increase plant growth rates and/or enhance cell division rates. The above-mentioned application further relates to a method for improving the growth of plants by overexpression of APC10 gene and/or its variants or repression of the SAMBA gene and/or its variants. The genes whose activities are changed in patent application EP2391642 are distinct and regulate, in cell cycle, processes other than those presented herein.